The proposed study is based upon our finding that certain polyribonucleotides have much greater potency as antitumor agents than the antitumor purines from which they are derived. An additional set of polyribonucleotides, prepared by enzymatic polymerization, will be used to test the hypothesis that these compounds are acting as polymeric drugs or drug delivery systems. A study of immobilization of various synthetic and degradative enzymes will be undertaken. These enzymes will be used in the synthesis and characterization of a carefully defined set of homopolydeoxyribonucleotides which will be evaluated as antitumor and antiviral agents. A comparison of the physicochemical properties of the DNA and RNA analog polymers will be made to reveal subtle differences in intra- and interchain interactions arising from conformational differences in the polymers.